The present invention relates to a procedure for automatically landing an aircraft, particularly an unmanned aircraft on a moving, particularly floating landing platform, for example, on an aircraft carrier. The invention further relates to a system for automatically controlling the landing of an aircraft on a moving platform.
The landing of an aircraft on a moving landing platform, particularly on an aircraft carrier, is difficult even for pilots of a manned aircraft. However, it is even more difficult to land an unmanned aircraft on a floating landing platform which is subject to constant wave motions. These wave motions may occur about the lateral axis as so-called pitching or about the longitudinal axis as so-called rolling. In the case of a combination of pitching and rolling, a movement about the vertical axis of the floating landing platform may even occur.
In addition, cross wind influences, not to be underestimated on water, may make the landing of aircraft on a floating platform more difficult. Particularly when landing remote-controlled unmanned aircraft, cross wind influences are very difficult to compensate.
As a result of the described movements of the landing platform about its three space axes and possibly along its three space axes, the landing threshold provided on the landing platform, which defines the intended landing spot, describes a constant movement about the space axes and possibly even along the space axes. This movement of the landing spot represents a considerable difficulty with respect to carrying out a precise-spot landing because the landing aircraft constantly has to be newly aligned.
Especially in the case of an aircraft carrier which, because of its length, hardly carries out motions about its lateral axis but, because of the height of its superstructure, is subject to a noticeable rolling motion about its longitudinal axis, the position of the intended landing spot as well as the relative position of the landing runway with respect to the longitudinal axis will fluctuate constantly with the frequency of the rolling motion. In the case of conventional approach procedures, this has the result that, because of the constant recorrecting of the attitude of the landing aircraft, the aircraft will fly a rolling course in the approach, whereby the danger of an imprecise landing or an aborting of a landing or even a crash landing will increase.
In practice, it is therefore first attempted to compensate the rolling motions of the ship by measures on board the aircraft carrier. In addition, a landing control officer (LCO), as a rule, is stationed on an aircraft carrier in the proximity of the landing spot. The landing control officer (LCO) has visual contact with the approaching aircraft, checks whether the aircraft is on the intended gliding path and conveys correction signals with respect to the aircraft attitude to the pilot by radio and by sign language. The landing of an aircraft on a moving platform, such as an aircraft carrier, is therefore very dependent on the capabilities of the crew of the aircraft and of the crew of the moving platform, so that automatic landings, as preferred for unmanned aircraft, have hardly been implementable.
It is therefore an object of the present invention to provide a procedure of the above-mentioned type for the automatic landing of an aircraft on a moving landing platform, by which safety during landing is clearly improved. Furthermore, a system for the implementation of such a procedure is provided.
In the case of the procedure according to the invention for the automatic landing of an aircraft, particularly of an unmanned aircraft, on a moving, particularly floating landing platform, such as an aircraft carrier, the aircraft being equipped with automatic navigation devices and an automatic landing control device, the following steps are carried out:
a) detecting the position data of an intended landing spot onboard the moving landing platform;
b) detecting of motion data of a motion of the landing platform about at least one of its space axes;
c) determination of at least one imminent point in time at which the landing spot takes up a reference position and preferably the landing platform takes up a reference alignment;
d) transmitting the point in time determined in Step c) as well as the reference position of the landing spot and/or the position data and motion data detected in Steps a) and b) and preferably also the reference alignment determined in Step c) to the landing control device of the aircraft;
e) controlling the aircraft such that the touchdown spot of the aircraft on the landing platform precalculated by the landing control device corresponds to the reference position of the landing spot and that the touchdown point in time precalculated by the landing control device, which corresponds to the point in time of the reaching of the touchdown spot, corresponds to the point in time determined in Step c).
By precalculating the point in time at which the landing spot takes up a defined reference position and preferably also the landing platform takes up a defined reference alignment, the motions of the landing platform can be ignored and the aircraft can carry out the approach at a constant attitude and on an essentially straight gliding path. The landing control of the aircraft therefore knows one or more points in time in the future at which the landing spot on the landing platform will take up a defined reference position, and also knows the coordinates of this (these) reference position(s) in an absolute coordinate system. The landing control can then select the flying speed over the ground and the rate of descent of the aircraft such that the touchdown spot computed from the actual position of the aircraft, the flying speed over the ground and the rate of descent as well as the height of the defined reference position of the landing spot at the computed point in time corresponds to the position of the landing spot in the space.
Since preferably the attitude of the aircraft as well as the reference alignment of the landing platform essentially correspond to one another at the point in time of the coincidence of the landing spot and the touchdown spot, thus at the moment of the touchdown, a soft landing of the aircraft on the moving landing platform can be predicted. As a result, a rolling course of the aircraft is avoided in the approach and the holding of the course of the aircraft in the approach is clearly facilitated, which is advantageous particularly for unmanned aircraft.
In a preferred embodiment of the procedure according to the invention, the cross wind influences can be reduced in that the longitudinal axis of the landing runway provided on the movable landing platform is turned into the wind before the landing.
Preferably, this alignment of the landing platform takes place continuously during the landing approach of the aircraft.
The reference position is preferably at least approximately horizontal. As a result, the touchdown of the aircraft on the landing platform can take place at a zero passage of the corresponding rolling motion about the space axis (axes), particularly about the rolling axis.
The procedure according to the invention is particularly effective when the space axis, for which the motion data are detected in Step d), is the longitudinal axis of the moving landing platform. As a result, the rolling motion of the landing platform can be neutralized for the landing approach.
Preferably, the space axis, for which the motion data are detected in Step b), is the lateral axis of the moving landing platform, whereby the pitching movement of the landing platform can be neutralized.
In another preferred variant of the procedure, the space axis, for which the motion data are detected in Step b), is the vertical axis of the moving landing platform, whereby a yawing motion of the landing platform is neutralized.
In a preferred further development of the procedure according to the invention, in Step b), also translatory motion data of the landing platform in the direction of at least one of the space axes are detected and are taken into account during the determination of the point in time in Step c) and these translatory motion data are transmitted in Step d) into the landing control device of the aircraft and are taken into account in Step e) when controlling the aircraft. For the landing approach of the aircraft, in addition to the neutralization of the motions of the landing platform about the space axes, a motion of the landing platform in the direction of one or more space axes can hereby also be taken into account, and this motion can thereby be neutralized.
The system for the automatic controlling of the landing of the aircraft on the moving landing platform controls the landing of the aircraft according to a procedure of the invention by position data of the landing spot provided on the landing platform, of motion data of the landing platform and/or of a previously determined point in time at which the landing spot will take up a reference position.
The landing control of the aircraft knows—as mentioned above—one or more points in time in the future at which the landing spot on the landing platform will take up a defined reference position, and also knows the coordinates of this (these) reference position(s) in an absolute coordinate system. The landing control receives these data or the information required for computing these data per wireless data transmission from the landing platform. The landing control also knows the actual position of the aircraft in the absolute coordinate system. The landing control will then select the flying speed over the ground and the rate of descent of the aircraft such that the touchdown spot computed from the actual position of the aircraft, the flying speed over the ground and the rate of descent as well as the height of the defined reference position of the landing spot at the computed point in time corresponds to the landing spot.
The controlling of the aircraft can preferably also take place while taking into account a predefined reference alignment of the landing platform at the reference point in time at which the landing spot will take up the reference position. If the reference alignment, for example, laterally of the approach direction is horizontal, it is thereby achieved that the aircraft can land horizontally, thus with a 0° roll angle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.